64 INSTINCTIVE BEHAVIOUR 
structure nor in the case of behaviour, that entertained by 
modern science. It is indeed an expression of opinion con- 
cerning the metaphysics of instinct. Leaving the question of 
ultimate origin precisely where it stood in the times of Addison 
and of Spence, modern science seeks to trace the natural ante- 
cedents of all natural phenomena, and regards structure and 
behaviour alike as the products of evolution, endeavouring to 
explain the manner of their genetic origin in terms of 
progressive heredity. 
Omitting, therefore, all reference to problems which, how- 
ever important, are beyond the limits of scientific inquiry,* 
we may take as a basis for further discussion Spence’s definition, 
according to which the instincts of animals are those faculties 
by which, independent of instruction, observation, or experi- 
ence, and without a knowledge of the end in view, they are all 
alike impelled to the performance of certain actions tending to 
their own well-being and the preservation of the species. 
Let us first consider the reference of instinctive actions to 
a faculty by which animals are said to be impelled to their 
performance. Paley also defined instinct as “a propensity 
prior to experience.” And unquestionably in the popular con- 
ception itis usual to attribute instinctive acts to some such 
conscious cause. But it will be more convenient, for the 
present, to consider instinctive behaviour from the objective 
point of view, as it is presented to our observation ; we may then 
proceed to the further consideration of the conscious con- 
comitants which may be inferred. From the objective point 
of view, therefore, we may agree with Professor Groos, who 
says t that “the idea of consciousness must be rigidly excluded 
from any definition of instinct which is to be of practical 
utility,” since “it is always hazardous in scientific investigation 
to allow an hypothesis which cannot be tested empirically.” 
In this we have the support of Dr. and Mrs. Peckham, whose 
studies of the life-histories of spiders and wasps are models of 
* Cf. supra, p. 18. 
+ “The Play of Animals,” translated by Elizabeth L. Baldwin, 
p. 62. 
